public class HardDisk extends Object{
     int amount;
     HardDisk() {}
     HardDisk(int amount) {
	this.amount = amount;
     }
     public void setAmount(int a) {
	amount = a;
     }
     public int getAmount() {
	return amount;
     }
     public String toString() {
	return "HD已覆盖toString";
     }
     public boolean equals(Object obj) {
	return true;
     }
}

